The brake discs of most wide-body commercial and military aircraft are made from Carbon-Carbon (C—C) composites. Traditionally, C—C composites used as friction materials are produced by combining carbon fibers with a carbon matrix material that is deposited around the fibers using a Chemical Vapor Infiltration (CVI) process.
Unfortunately, this CVI process is expensive, capital intensive and is a time-consuming process, frequently taking several months to complete. Therefore, several attempts have been made to reduce the cycle time and costs associated with CVI processing by using lower cost pitches together with VPI and RTM processes. The problem with using these densification processes is the length of cycle time (typically about 5 cycles) and low final densities (often less than or less than 1.75 g/cc. Also, coal tar pitch feedstocks exhibit high variability in properties and composition that may cause variation in the properties and performance of the carbon-carbon composite.
This invention describes a method to produce C—C composites with improved density (about 1.8 grams per cubic centimeter or higher) and associated properties (mechanical and thermal) as well as friction and wear performance.
Background prior art includes the following documents: U.S. Pat. No. 7,172,408 B2, entitled RAPID DENSIFICATION OF POROUS BODIES (PREFORMS) WITH HIGH  VISCOSITY RESINS OR PITCHES USING A RESIN TRANSFER MOLDING PROCESS; US 2006/0261504 A1, entitled CARBON-CARBON COMPOSITE PREFORM MADE WITH CARBON FIBER AND PITCH BINDER; US 2005/0266118 A1, entitled PROCESS AND APPARATUS FOR THROUGH THICKNESS INFILTRATION WITH MOLTEN RESIN; US 2004/0195712 A1, entitled DELIVERY OF PITCH/THERMOPLASTIC/THERMOSET RESINS IN RTM SYSTEMS; EP 173292 A2, entitled CARBON FIBER PREFORM DENSIFICATION BY PITCH INFILTRATION FOLLOWED BY RESIN TRANSFER MOLDING; and WO 2005/116476 A2, entitled REUSABLE CORE CARBON-CARBON COMPOSITE BRAKE DISC.
US 2006/0261504 A1, entitled CARBON-CARBON COMPOSITE PREFORM MADE WITH CARBON FIBER AND PITCH BINDER, claims a process for producing a carbon-carbon composite preform which comprises: providing short carbon fiber segments or short carbon fiber precursor segments; providing pitch in particulate form; combining blend comprising the fiber segments and pitch particles in a mold; subjecting the resulting mixture of fibers and pitch in the mold to an elevated pressure ranging at a temperature above the melting/softening point of the pitch to create an uncarbonized preform; cooling the preform to below its softening point and removing it from the mold; placing the preform in a constraint fixture; and carbonizing the combined components in the constraint fixture at an elevated temperature for a period of time of sufficient to provide a preform having a density in the range 0.8-1.6 grams per cubic centimeter.
U.S. Pat. No. 6,323,160 B1, entitled CARBON-CARBON COMPOSITE MATERIAL MADE FROM DENSIFIED CARBON FOAM, discloses a carbon-carbon composite material made by providing an open-celled carbon foam preform and densifying the preform with carbonaceous material. The open-celled carbon foam preform may be oxygen stabilized prior to carbonization, and the foam preform may be densified by CVD, HIP, PIC, VPI, pitch and resin injection, or any combination thereof. The carbon-carbon composite material may be heat treated to provide thermal management materials, structural materials, or a friction material for use in a brake or clutch mechanism. 